Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates generally to motorized wheelchairs and more particularly to the motorizing apparatus in the under carriage that includes the support, drive and positioning control mechanisms of the wheelchair. Specifically, this invention relates to an improvement in the motorizing apparatus of the wheelchair which facilitates the navigation of stairs, irregular terrain or other obstacles.
2. Description of the Prior Art
In the prior art, wheelchairs have often used motorized drives on the rear wheels, and typical prior art systems are disclosed in U.S. Pat. No. 5,477,935, U.S. Pat. No. 5,197,559 and U.S. Pat. No. 5,161,630. Prior art steering has been accomplished by means of inducing a speed differential between two rear wheels, or alternatively, as disclosed in U.S. Pat. No. 6,334,497, a pivoting front wheel is used for steering.
While these prior innovations greatly aided the person in the wheelchair in achieving improved mobility, the operator was still confronted with the difficulty (or impossibility) of traversing rough terrain and navigating obstacles or stairs. One of the problems confronting the wheelchair operator was that regardless of the drive mechanism, the wheelchair would be unstable and lose traction when attempting to navigate large obstacles or stairs. This problem naturally restricted most prior wheelchairs to flat terrain and required the occupant to seek assistance when confronting rough terrain or stairs.
Some prior art wheelchairs attempted to solve the stair climbing problem. In U.S. Pat. No. 6,328,120 and U.S. Pat. No. 5,513,716 apparatus is described which uses climbing arms that extend from the wheelchair to lift the wheelchair from one stair to the next. While these prior art wheelchairs theoretically could climb stairs, they did not eliminate the dangerous instability and loss of traction of the prior art, and they did not present a safe solution for generally traversing all obstacles and stairs.
The present invention solves the aforementioned instability and slippage problem for the wheelchair and allows the operator to safely drive the wheelchair up and down stairs and over large obstacles and rough terrain. This is accomplished principally by the use of dual, articulated, front and rear, driving treads. This tread drive is used to provide the necessary traction, and the mechanism used for positioning the tread drive also assists in controlling the wheelchair disposition. In addition to the tread drive, front support wheels are used to raise and lower the front of the wheelchair, and rear drive wheels are used for both drive traction and steering. In a further feature of this invention, a mechanism is disclosed for providing swivel steering capabilities to the rear drive wheels.